Endless digger type mine dredger



J. L. ROE

ENDLESS DIGGER TYPE MINE DREDGER May 20, 1952 1 hm O wm mm wm Nm mm, Q sw wm R.,/ L@ Q H %.Q\ Wmv NA N mmv WQ w QW n N R .R N O m IJ l A FiledNov. 1. 194'? Filed Nov. l. 1947 May 20, y .J'L' ROE ENDLESS DIGGER TYPEMINE DREDCER' 3 Sheets-Sheet 2 v vE/vroR, JONAS L. Q05,-

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May 20, 1952 J, ROE

ENDLESSYDIGGER TYPE MINE DREDGER 3 Sheets-Sheet 5 Filed Nov. l. 194'?Z'A/ VE/ ro R, JONAS L. Q0

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Patented May 20, 1952 STATES. P

TENT Quandro Mining & EquipmentCorp., a corporationof CaliforniaApplication November 1, 1947,l Serial No. '783;564

pClaims.. 11v

The presentl invention relates to dredgers. Particularly the inventionhas for an object the provision of" a dredgeradapted for tunneling,breasting and general excavation in drift-channel types of'v mines. Theinvention eliminates the use of drilling, blasting and manualhandling ofmaterialgunder ground:

The invention has for an object Ythe provision of a dredger which isparticularly adapted for themining ofrninerals. The device functions toremove the ground' andto separate thenes or shipping ore from the wasteor tailings.

As an, example of how a device incorporating the invention may be used,it; is customary to irstl cutpinto the hillside and formfa main tunnelwhich may have aslight slope. Thereafter cross cuts1 are madewhichinterconnect theA main tunnel, The present invention s-tarts withthe end ofi av cross lc ut at what isV termed the breast. As the-dredgeroperates, ore which is beingY removed is. sorted by the device of' theinvention, the fines being directed' rearwardly of` the devicefor-.movement outwardlyv of; the mainl tunnel while the tailings arebuilt up adjacent. the breast. In this manner a tunnel4 isformed-andbuilt against the hreastatsnbstantially the same time so thatthe removedl cut is relled; This is known as the retreating methodK oftunnelling or dredging, I t 0f. QQurse, understood that the earth. priorto tunnelling has beenoompacted' by nature. The tunnelling operationbreaks upthe earth. However, the refilling is such as to restore theearth substantially to, its original condition prior to c ompacting, Inthe typerof operation performed the. device operates upon minerals whichare to be. mined andl a` method is followed wherein the graveljismixedwithweter as is likewise the tailings.. As.. rule. experience.has shown that e13- proximately 3,51% of thegravel' is removed to thesurface for processing.

An objectof theinvention is the provision ofa dredger whichprogressivelytunnelsthe earth formation in a simple and. expeditious manner- AfurtherObjectis the provision efe. dredging machine incorporating a novel. ferm0.1V boem which is ener ted a positive. manner and Whereby. tlfieboomlmay b e raised; loweredV or turned to the right or ljet without they useof cables, jib arms, the. like.

A further object is the provision of a dredging machine incorporatingahydraulic means which is positivein its operation and adapted tocontrol operation of a boom.

A further object, is the provision ina dredging machine of means whichclassifies on the job the oredredged,3

A further object is the provisioningJ dredger of aboom having. a bucket:line adapted to be drivenin a positive manner.

Another object is the provision` in. a. dredger o f an eicient type ofmounting for aY boomA and whichpermits the boomfto be easilymoved;

A further object is the provision of a dredger construction whichpermits easy assemblage, of the various parts, which is, eilicientinopera-tion and. generally. superior to dredgersnow known to theinventor.

With the above mentioned and` other. objects in View, the inventionconsists. in thenovel` and useful provision, formation, construction,association and relative arrangement offparts, members and features, allas shownin one embodiment of the invention in theaccompanying drawings,described generally and more particularly. pointed out in the claims.

In the drawing-s:

Fig. 1 is a fragmentary side elevation. of.L the dredger` oftheinvention shown in the act. of excavating earth;

Fig. 2- is a transversesectional view on theline 2-.2 of Fig. 1,showingl the. portions of.V the boom and its operating mechanism;

Fig.A 3 is a fragmentary4 plan. view partially. in section,schematically showing the hydraulic system for operatin'gthe boom,together with an electrical circuit for motors associatedy Withthehydraulic system, the saidviewbeing taken substantially on the line3--3` of Fig. 1

Fig. 4 is a fragmentary elevation looking substantially in the directionof the arrows on line -l of Fig. 1;

Fig. 5 is a fragmentary sectional view on the line 5 5 of Fig. '7;

' Fig. 6y is a fragmentary sectional View on the line 6 6 of- 5; Fig. '7is a sectional view on the line 1.-] of Fig. 5; l

Fig. 8 is 'an end elevation of the/invention looking towardtheboomofFig. l;

Fig. 9 is a fragmentary View of ther dredger in the act of` tunneling,and showing movement of certain members thereof in one plane;l and,

Fig. 10-is a plan View of the showingin Fig. 9, and illustrating thesweep of an element ofthe dredger in a transverse direction.

Referring` now withv particularity to thedrawings, the dredger lincludes a tractor 2A mounted on a pair of endless chains' 3 and` 4,which are ordinarily called Gaterpillars the chains being driven in anysuitable manner for the purpose of propelling the vehicle4 forwardlyAor` backwardly, together. with a boom 5 atoneend of the tractor,

which boom includes a bucket line designated generally as 6, the bucketsbeing of the excavating type and which boom, through mechanismdesignated generally as 1, is capable of being raised or lowered andswung on an arc, together with means 8 adapted to classify or separatecertain sized ore from tailings or waste material, all of which meanscooperate in the performance of a dredging operation.

While the dredger as an entirety has the appearance shown in Figure l,still no particular type of tractor or framing is contemplated. It isexpected that a framing in a device of the character of this inventionshould be rigid in structure and adapted to resist stresses of largemagnitude. As shown in Figures 5 and '7, the tractor, as to its framing,includes -a pair of spaced-apart side Walls 9 and I0, a bottom or basewall I I, and a top wall I2,both of which interconnect the side walls.These walls are brazed, welded, or otherwise secured in cooperativerelationship.

The framing also includes end walls I3 and I4. the end walls are rigidlysecured to top wall I2 in any approved manner, such as by welding. Theend walls and side walls 9 and I0 extend above the top wall I2. Thisprovides a space to confine other mechanism utilized in the practice ofthe invention, as hereinafter detailed.

The means 8, utilized for the purpose of classifying the ore,constitutes a trommel in theV form of a perforated drum I5. This drumhas annular end members of reduced diameter shown at I6 and I1 which aresecured to the main drum structure by annular flanges.l The end I6 ispassed through an enlarged opening in the end I3 of the framing whileend I1 thereof is passed through openings in a pair of members I8 andI9. The arrangement is such that the trommel is supported on rollers atboth ends. For instance in Figure 6, a pair of rollers and 2| havetrunnions passed between end wall I3 and a wall 22, the rollers being inengagement with the periphery of the reduced diameter member I6 of thetrommel. The opposite supporting means for the trommel follows the samepractice in that the rollers shown engage the periphery of the reducedend I1 of the trommel. These rollers are interposed between members I8and I9 and held therebetween by means of trunnions.

whereas members I8 and I9 are removable from said frame so as to permitthe trommel to be inserted within the frame and rotatably held therein.

The members I8 and I9 are held separated by an annular spacer piece 23,which spacer piece is provided with a flange 24. The end wall I4v has anenlarged opening and the flange 24 is adapted to be secured by bolts 26to said end wall. The construction is such that end Wall I9 ts withinthe enlarged opening 25. Thus the walls I8 and I9 are removable as aunit With the opening 25 of such size as to permit ready passage of thetrommel therethrough. The trommel is surrounded by a trommel casing 21of circular form, said casing is welded or otherwise secured to endWalls I3 and 22. The opposite end of said trommel casing is xedlysecured to the end Wall I4. Thus by providing framing top, bottom andside walls, together with the trommel casing, all secured together instress-resisting relationship, a rigid frame structure results.

The perforated drum I5 of the trommel externally carries helical blades,blades 28 being It is to be v observed that end wall I3 is fixed to theframe,

pitched opposite to blades 29 for a purpose hereinafter set forth. Thetrommel drum is internally provided with a helical blade 30 which ispitched in one direction and extends between the ends thereof. It may bestated that the reduced diameter portion I6 is the inlet end for thetrommel and reduced diameter portion I1 is the outlet. The externalblades on the trommel are adapted to direct fines to a given location inthe trommel casing 21. A motor 3|, is positioned on the top wall I2adjacent the end Wall I4. The motor s'haft'32` carries a sprocket, notshown. The'reduced diameter portion I1 of the trommel drum is providedwith a sprocket, not shown, and a continuous chain 33 is passed aroundthe sprockets aforesaid for the purpose of rotating the trommel.

A trough 34 is inclined downwardly Within the reduced end I6. Thistrough is used for feeding ore within the trommel and to assist in saidfeeding the trough is formed to carry a valved pipe 35 through whichWater, under high pressure, is directed against any ore received on thetrough for reception within the trommel.

Positioned beneath and depending from the base member II is a casing 35.This casing is in direct communication with the interior of the trommelcasing. The bottom wall II and trommel casing 21 have axially alignedopenings at 31 and 38 with a wall extending between said members andsurrounding the openings. The casing 36 is adapted to house a pair ofintermeshing bevel gears 39 and 40, bevel gear 39 being mounted on ashaft 4I suitably journalled in the casing with one end of said shaftcarrying an mpeller blade 42. Gear 440 is passed through the side wallof the casing and is mounted upon shaft 43 of a motor 44, the motorbeing external of the casing and secured to the bottom Wall II. Thecasing 36 is involute in form and has its outlet at 45 (see Figure l).The outlet is in communication with a flexible hose 46. By way ofexample, when ore is fed into a rotating trommel, the nes of a givensize will pass through the perforations in the trommel and be receivedupon the inner Wall surface of the trommel casing. The helical externalblades 28 and 29 will move this material toward the opening whichcommunicates with the casing 36 and the impeller blade Will then directthe material so received therein to the outlet of said casing and intothe flexible hose. It is obvious that the casing 38 together with theimpeller therein and the means for rotating the impeller constitutes oneform of sand pump. That material which is received within the trommeland does not pass through the perforations thereof is directed outwardlyof the trommel through end I 1, being fed by the helical blades 30.

In the practice of the invention, water is used and I provide a pipe 41which is axially passed through the reduced end portion I1 and into thetrommel. The pipe is provided with a series of perforations 48 wherebyWater may be sprayed on the ore received within the trommel.

The boom 5, with its associated bucket line, is adapted to be moved invarious directions so as to perform, in an eiiicient manner, an earthdigging or tunnelling operation. This boom is mounted in a gimbal 49,the gimbal being substantially rectangular in form (see Figure 4), thegimbal having side members 5U and 5I interconnected by top and bottomtransverse pieces 52 and 53. The top and bottom transverse pieces arecentrally provided with studs 54 and 55 which are receivedinf bearingscarried by top and bottom gimbal supports 56 and 51. The bottom support51 is secured toithe bottom wall I I, while the topsupport '6 is securedbetween the end wall I3 and the side walls-9 and I0. As shown inv Figure1, the-supporte may have offset portions so as to permit the gimbal toreadily rotate between said supports.

TheY boom 5 is mounted in the gimbal 89 at one end thereof; The boom 5includes a pair of spaced-apart elongated side plates 58 and 259 bracedby a longitudinally extending, centrally positionedk rib 6I), the saidrib provided with transverse end pieces lil and 52, which extend betweenthe side plates. The rib, the transverse pieces, and the side plates areall rigidly secured together. Adjacentv the outermost end of the boom,and provided in` each side plate, are bearings 63 and 84 adapted torotatably support therebetween a shaft'65. Positioned between the sideplates 58 and 59 and carried by the shaft 65 are. sprockets 66 and 61.The opposite end of' the boom has the side plates 58 and 59r thereofprovided with bearings 68 and 69, carrying a shaft 18'. Mountedvexternally of the side plates 58 and 59 are gears 1I' and 12. The sides58 and 5I of; the gimbal are positioned between the side plates oftheboom and a gear, as best shown in Figure 4, the gimbal being providedwith bearing portions through which the shaft 1i) is passed. Sprockets13' and 14 are mounted on shaft 18, which sprockets are in substantialparallelism with. sprockets 68 and 61. Forward of the transverse piece62T are a pair of axially aligned shafts 15' andY 15'. These shafts arecarried in suitable bearings provided in the side plates '58 and 59;.and. gears 11 and 18 are carried on ends of said respective shafts, thegear 11 being in mesh with gear ISI while gear 18 is in mesh with gear12. Carried on the shafts 15` and 16 and within the confines of the sideplates 58 and 59 are bevel gears. 19 and 88, these bevel gears being inmeshv with further independent bevel gears 8I- and 82. Bevel gears 8|and 82 are carried on shafts of motors 83 and 84. These motorsaremounted in any convenient manner between the rib 68- and the sideplates. It will be observedthat each motor, when in operation, drives ashaft, whichY independentA shafts 15 and 16 in turn cooperateto drivethe single shaft 18. The advantages of this construction will bedetailed in the statementv of the operation.

Extending between both ends of the boom and over the sprockets 66, 61and 13, 14 is the bucket line 6. The bucket line includes buckets 85which are spacedly secured by solid links 86. IThis bucket line isconventional, and the said links thereof' are joined together in theusual manner, such as best,` illustrated in Figure 2, that is to say,`by means of pins passed through knuckles in both the links and thebuckets.

The buckets are of the excavating type,l which is to say that a sharptooth or teeth portions 81 are provided. for each bucket, which teethcut thev earth formation and deposit the same in the scoop portion ofthe bucket and hold it therein during travel of, the bucket to, in turn,deposit such formation onto the trough 34. No particular form of the.bucket is contemplated, as buckets. arel common in the art.

The mechanism 1 for; controlling movement of the boom is` detailed inFigure 3. Positionedbetween the.v trommel casing 21Y and the bottom. andside wallsr of the tractor are elongatedl cylinders 6. 885 and 89. wallIi3.

Each cylinder has an intermediate division wall. 98'. and 9i'. Eachcylinder' forward of its division wall", toward the end wall I3, isopenended' while a` second portion of. the cylinder is closed orprovided with a head at 92 and 953. For convenience of' description, theopen-end portions as applied to each cylinder are designated as Qliandand the closed portions as. 96 and 91. Within the, closed portions ofthe cylinders are pistons 9i; and' 99 and within the open-endedportionsof each cylinder are cross-heads l 88 and Ii". Piston rodsdesignated generally as m2 interconnect the respective cross-heads witha piston= and said rods are passed through the division walls 88 andSBI- as shown in the figure. Each cross-head has` a socket portion EMS.Arms Iii and F85 are secured to side plates 58 and 59, each arm at oneend carrying a socket ISE, 81. Links Hi8 and its are provided with ballends, as for instancel illustrated at Il, which ball ends are positionedbetween the sockets of the cross-heads and the arms. It is evident thatmovement of the links will swing thev arms IM and IE5 to in turn causemovement of the boom, as hereinafter set forth in the statement ofoperation.

A hydraulic system is utilized for actuating the pistons in thecylinders, which system is shown diagrammatically in Figure 3. I preferto use a closed system and accordingly, I provide independent pumps ofany type. In the drawing two gear pumps HI and HZ. are provided. A pipeiii-3 communicates with one end of cylinder portion 8S, the opposite endthereof being in cornmunication with pipe II leading to either theintake or outlet opening of the gear pump. Pipe II. connects with acheck valve I i5, which check valve in turn communicates through pipeIIS with a tank ill and likewise with a check valve H8. Check valve IISthrough the medium of pipe I I9 connects with the pump at the oppositeport thereof, which may be either intake or outlet, and with theopposite end of the cylinder portion e5; Without detailing further, itmay be said that the same procedure is followed for the oppositecylinder portion, it being noted that the pump H2 has check valves onopposite sides thereof and that the line H55 communicates with the saidcheck valves. Electric motors It@ and I2-I- may drive their respectivepumps by any suitablemeans. Each electric motor is in circuit with areversing switch |22 and |23, the reversing switches leading toloverload circuit breakers igt and' H25, the said switches and the saidcircuit breakers in turn being connected with a source of power supply.

The operation., uses and advantages of the invention are as follows:

It is intended primarily that the Caterpillar cr tread portions 3 andshould be positioned beneath the tractor frame rather than in theposition shown in Figure 3. This will permit a greater swinging of theboom. To operate the boom in the manner depicted in Figures l0 and ll,the motors I2@ and I2! are energized upon the throwingk of the reversingswitches in one or the other direction, it being intended in the presentsystem that the pumps III and II2 should be reversed as to operation andas to the direction in which fluid is passed through the respectivepipes. rlhe tank I i1 is filled with hydraulic fluid andv initially theclosedv portions S5 and 91 ofv the cylinders arelled with fluidY on bothsides of. the pistons se and 89. To prevent leak, pack- Each cylinderterminates in end ing is provided in the division walls 90 and `9| atthe zone of passage therethrough of the piston rods. The cross-heads inthe open-ended cylinder portions 94 and 95 stabilize the thrust on thelinks |08 and |09 and likewise that on the piston rods |02. If the boomis positioned centrally of the tractor frame, and it is desired to raisethe boom from its lowered position of Figure 10 to its upper position asindicated by the dotted line position thereof, hydraulic fluid is pumpedbehind each piston, that is to say, into the space included between therespective pistons 99 and 99, and the end walls or heads 92 and 93. Asfluid lls the space between the pistons and the division walls 90 and9|, it is necessary to bleed this fluid. Hence, assuming proper rotationof each hydraulic pump, the fluid is removed from one side of eachpiston and directed through the pipes, assu-ming one side explanation,into pipe |20 through the pump into pipes ||4 and ||3 rearward of thepiston. The other side is operating the same way, with the result thatthere is a direct thrust upon the piston rods and the associated linkswhich interconnect the arms |04 and and the boom will be moved upwardly,the boom revolving on the shaft 10. To swing the boom transversely or onan arc, as illustrated in Figure l0, one of the reversing switches isthrown, say the switch at |23, whereupon fluid included between thepiston 99 and the head 93 is removed or bled and passed to the otherside of said piston or between the piston 99 and the wall 9 l. This isaccomplished by reversing the direction of movement of the motor, whichreverses the movement of gear pump ||2. The operator need not watch theboom movement, as when the boom has swung its full arc, the overloadcircuit breakers |24 and |25 will operate and brea-k the circuit. In theevent that the piston in one or the other of the cylinders does notcomplete its stroke, one or the other of the one way check valves in thepipes ||4 and ||9 will open and direct fluid into the line from thetank 1. After suicient iiuid has been obtained the check valves willclose. is being removed from one end of the cylinder and directed to theopposite end, that there is a negative pressure on one side of the lineand a positive pressure on the other. If this negative pressure is lessthan atmospheric, a check valve will open and admit liquid from thesupply tank. If we assume that the sweep of movementy for the boom is ata lower level or in the plane of the solid lines for the said boom,shown in Figure 10, the boom may be held in this position during a sweepby reversing the turning direction of both motors |26 and |21 uponoperation of the switches |22 and |23. Liquid is directed behind one ofthe pistons under pressure, whereas the opposite cylinder removes fluidfrom behind a piston and directs the uid under pressure forwardlythereof. This swings the boom. If it is also desired to raise the boom,one or both pistons are moved forwardly to a given position. If a singlepiston is moved forwardly to a given position, and the other pistonretracted, the boom will be brought to a given level and turned,depending upon which piston is actuated. I, therefore, have completecontrol of boom movement with a device that does not incorporate cables,jibs, or other projecting members, and one ythat is simpler to operateand more positive in its action.

As illustrated in both Figures 1 and 8, the arms |94 and |85 are curvedin part and secured to the side plates of the boom adjacent the low- Itis evident that when liquid j 8i ermost edges thereof. This constructionaffords for leverage so that the device will readily lift the boom aswell as swing the same. Y Y

The motors 83 and 84 may be of small size and positioned between the rib6i) and a side plate. Thus, the boom is stabilized by this constructionand a large single motor is unnecessary. Movement of shaft 19 iscontrolled by the independent motors which revolve the independentshafts 15 and 16. This construction, in actual practice, givesiiexibility to the structure and permits proper movement of the bucketline, particularly when the bucket line is engaging formation which isdiicult to cut. The buckets excavate the formation, as 'shown in Figure1, and carry the formation along the upper course of the continuousbucket line, the buckets finally depositing the ore onto the trough 34for reception within the trommel. During movement of the bucket line,the trommel is being rotated by motor 3|, motor 44 is energized torevolve the impeller 42, and Water is being forced under pressurethrough line 35 over the trough, while at the same time, water is beingpassed through pipe 41, through openings 4.8, and into the trommel. Pipe41 is eccentric to the axis of the trommel so as not to interfere withore received therein. I provide a pair of pipes at |26 and |21 which aresecured to the trommel casing, as shown inrFigure 7, and which pipeshave openings communicating with openings in the trommel casingthroughout its length. Pipes |26 and |21 communicate with a source ofwater supply. Thus', as the ore is removed and carried by the bucketline, and dumped onto the trough, water under pressure through line 35aids in directing such ore within the trommel. The trommel, as itrotates, will feed the ore therein from one endthereof to the other,through the medium of the blades 30, and the nes of a certain size willpass through the perforations of the trommel and be received in thespace included between the periphery of the trommel and the innersurface of the trommel casing. The oppositely pitched blades 23 and 29will feed the material in this spaceV toward the opening whichcommunicates with theA casing 36, to be acted on by the impeller 42,'and thence directed from said casing 36 rearwardly of the dredgerthrough the flexible hose 46. The tailings of a size not sufficient toallow passage through the perforations are fed outwardly of the trommelthrough the reduced diameterportion i1, and the flared outlet mouthmember |28. Finally, I may protect motor 3| by providing a cover |29,carried by the framing.

I have heretofore detailed in the preamble, a method of removing ore byforming a rst out or main tunnel in the side of a hill, followed bymaking cross cuts, and then cutting the formation adjacent the breastand by a retreating method, removing the fines and building up thetailings against the breast. The tailings are directed so as to buildupagainst the breast in each case, whereas the fines are directed throughthe exible hose 45 for disposition outside the tunnel, the said hosebeing laid adjacent the main tunnel so that the flow will be outwardlyof the hill. In mining operations of the character contemplated for thisinvention, substantially 35% of the gravel which contains the nes isremoved, the remaining percentage largely being tailings or rejects. Itis the gravel that is desired as it contains the minerals. For thisreason, a suicient quantity of water is used for mixing with thetailings and the gravel.

The Caterpillar or tread portions are operated in the usual manner sothat the tractor is at all times moved in accordance with the desires ofthe operator. The device functions rapidly to cut the formation, toseparate the gravel from the tailings or rejects, is of easy operation,and not particularly tiresome to an operator. The operator simply movesswitches in one or the other direction to actuate the motors driving thepumps, while other switches control the operation of the bucket line. Noparticular skill is required, and the operator may stand at one side ofthe tractor and watch operation while tunneling proceeds.

I claim:

1. A dredger including a tractor frame; a gimbal at one end of saidframe; upper and lower gimbal supports secured to the frame whereby thegimbal may rotate on a vertical axis; a shaft mounted on said gimbaltransverse to the mounting axis thereof; a boom mounted at one end onsaid shaft; hydraulic means for swinging the boom vertically on saidshaft and transversely upon rotation of the gimbal; said hydraulic meanscomprising a pair of cylinders, a piston for each cylinder, separatehydraulic pumps, and flow lines leading from said pumps through bothends of the cylinders, the said pistons being connected to the boom.

2. A dredger, including a framing; a gimbal mounted for movement in saidframing; a boom mounted for vertical swinging movement in said gimbal,said boom provided with a continuous excavating bucket line; a pair ofspaced-apart hydraulic cylinders mounted in said framing, a piston withits arm for each cylinder, links swivelly connected at one end to eachpiston arm, and at the opposite end swivelly connected to the boom, andmeans for hydraulically controlling movement of the pistons within saidcylinders whereby simultaneous like movement of both pistons in one oftwo directions vertically swings the boom, and movement of one pistonswings the boom transversely.

3. A dredger, including a framing; a gimbal mounted for movement in saidframing; a boom having side plates mounted for vertical swingingmovement in said gimbal, said boom provided with a continuous excavatingbucket line; and hydraulic means for swinging the boom vertically andtransversely comprising a pair of cylinders, each cylinder having: a4closed end and an intermediate wall forming a cylinder head .betweenwhich wall and the closed end is positioned a piston, that portion ofthe cylinder out-- ward from the intermediate wall being open ended, apiston arm extending through the intermediate wall, a cross head in theopen end of the cylinder, secured to said piston arm; an arm for eachside plate of the boom, and separate links swivelly connected at eachend between an arm and a cross head, simultaneous movement of thepistons within the cylinder in one of two directions swinging the boomvertically upon the shaft, and movement of one of said pistons in one oftwo directions turning the gimbal to move the boom transversely.

4. A dredger, including a tractor framing, a gimbal and gimbalsupporting means secured to said framing, a yboom provided with sideplates, a shaft transversely carried by said gimbal and securing one endof said boom, and a pair of motors carried between the side plates ofthe boom for independently and simultaneously rotating the said shaft.

5. A dredger, including a tractor framing, a gimbal and gimbalsupporting means secured to said framing, a boom provided with sideplates,

a bucket line positioned between the side plates, a V

shaft carried by said gimbal and securing one end of said boom, a pairof axially aligned shafts carried between the side plates, separatemotors for driving each shaft and gearing between each axially alignedshaft and an end of the firstnamed shaft, and means on said first-namedshaft for producing movement of the bucket line when both motors areenergized.

JONAS L. ROE.

REFERENCES CITED The following references are of record in the lze ofthis Ipatent:

UNITED STATES PATENTS Number Name Date 750,005 Quertier Jan. 19, 1904884,960 Suiter Apr.114, 1908 1,859,659 Elliott May 24, 1932 1,948,606Weining Feb. 24, 1934 2,131,189 Osgood Sept. 27, 1938 2,320,196 Roe May25, 1943 2,323,493 Sloane July 6, 1943 2,489,635 Gruber Nov. 29, 1949

